Solutions including a surfactant, such as hand soaps, body washes, shampoos, dishwashing liquids, and contact lens cleaning solutions, are being distributed in the market as contained in a predetermined container. Such a solution is typically foamed due to effects of the surfactant contained therein. The foaming solution envelopes an object to be cleaned and removes oil stains from the object without damaging the object. Specifically, the solution is in foam form when used for cleaning, while it is in liquid form when distributed or used for storage. Considering ease of use, there have been made some proposals on a container that allow a liquid to be supplied in foam form from an outlet of a container.
Discharging a solution in a container requires making the internal pressure higher than atmospheric pressure. For example, there are known so-called aerosol containers, where a gas for pressure increase is previously encapsulated. However, aerosol containers are sometimes questioned in terms of environmental problems, effective use of resources, or the like, since CFCs, propane, or the like are used as a gas for pressure increase. Further, there are many problems when the user reuses an aerosol container that the user has used on hand. On the other hand, there have been made proposals for increasing the internal pressure of a container using a manual pump, piston, or the like, including the following: (1) A proposal on a trigger sprayer where the cap of a nozzle assembly rotates around three positions: stop, spray, and foam (Patent Document 1); (2) A proposal on a nozzle which can select among continuous flow, mist, and foam in a trigger sprayer where a spray pump is attached to an opening of a bottle-shaped container and that sucks up a content liquid to a liquid chamber by depressing and releasing the spout of the spray pump during use and sprays the content liquid out of the spray outlet of the spout (Patent Document 2); (3) A proposal on a discharge mode selection device of a trigger pump dispenser which can select among all discharge modes: straight forward-flow, swirling, and foam, and causes no disturbance to each discharge flow (Patent Document 3); and (4) A proposal on a trigger liquid discharge device which allows the user to easily position a nozzle cap by means of a touch of a finger tip, a color or pattern based on vision, or the like in selecting the desired spray state of a spray nozzle (Patent Document 4).
These trigger sprayer devices have ease of use and are preferable to aerosol containers in terms of environment problems. However, trigger nozzles have problems to be solved in terms of the structural complexity thereof. Further, trigger nozzles can raise the proportion of the cost of the container or the like in the total price, although the solution is the purpose of the sale.
In view of the foregoing, as the most simple means for increasing the internal pressure of a container, there are so-called squeeze bottles, which discharge a content liquid by grasping the container and thus deforming it. Methods for selectively discharging foam or liquid from such a squeeze container include the following proposals: a proposal on a nozzle for both foam and liquid where a foam spray outlet communicating with the interior of a container body, and a liquid spray outlet are formed separately and where an outer lid for closing the foam spray outlet and the liquid spray outlet is rotatably inserted into an inner lid (Patent Document 5); and a proposal on a switching valve configured so that a liquid can flow from upstream to downstream when the container is uptight and cannot flow from upstream to downstream when the container is inverted (Patent Document 6). The above-mentioned proposals are common in that a ball-shaped valve is present on a channel for a liquid and that a liquid is selectively sprayed when the container is uptight or inverted. Further, the proposals have a simpler structure than trigger containers. Furthermore, since which of foam and liquid is to be discharged is determined based on whether the container is uptight or inverted, the proposals have an advantage in that selection of foam or liquid is clear. However, the user is required to handle the container in different orientations or in different ways. Accordingly, the feeling of use can be impaired. What is particularly inconvenient is that in the handling of small contact lenses, it is difficult to place foam discharged from the uptight container onto the lenses correctly.
A study on such containers for a foaming liquid, “Features of Foamer Containers and Recent Technical Trend” (Non-Patent Document 1) states “As consumers raise awareness of safety and resource saving, non-gas type foamer containers (referring to trigger bottles or squeeze bottles) have ease of use and can be said to be containers matching these days. Large products have been commercialized in the fields of hand soap and the like. The name recognition of foamer containers is being increased among consumers. To further increase foamer containers, I believe that it is necessary to repeatedly improve foamer containers in accordance with consumer needs.” It is important to propose new foamer containers in accordance with the diversification of consumer needs in the market.